Who said "The future is not fixed."?

This quote is attributed to Palpatine.

The future is not fixed. - Palpatine

"The future is not fixed."

Palpatine

"Did you ever hear the tragedy of Darth Plagueis the Wise?"

"The dark side of the Force is a pathway to many abilities some consider to be unnatural."

"Have you ever heard of the tragedy of Darth Plagueis? I thought not."

"Unlimited power!"